4957 20200831131513.0 PERIO-2020-0003 Van Camp, Michel IAG Newsletter 2020 Monthly IAG Newsletter 253 (August 2020) 25 years of continuous measurements of gravity in Membach On August 4, 2020, the superconducting (or cryogenic) gravimeter has been measuring for 25 years the variations of gravity with a precision of one-hundredth of a billionth (10-11) of g (g = 9.81 m/s²). Since September 18, 2017, this instrument holds a double world record, in gravimetry and physics: 1. Record of the cryogenic gravimeter that has operated the longest at a given location. 2. It is also, as far as we know, the longest levitation of a superconducting artefact in a magnetic field. This field is generated by persistent currents, which were injected in 1995 into superconducting coils, where they circulate since then without any resistance and therefore, without ever having been dissipated. Although this record does not contradict what physicists specializing in persistent currents expect – in theory, a superconducting current can flow forever –, it is at least worthy of a place in a "cabinet of curiosities". NO Membach Superconducting gravimeter 25 years World record michel.vancamp@observatoire.be https://www.iag-aig.org/iag-newsletters/253 NEWSLETTER